High-frequency signals, in the form of electromagnetic waves, are frequently emitted by antenna units which are formed on circuit boards and include antenna elements, such as microstrip antennas. Usually, a preferably large surface area of the antenna unit, relative to the surface area of the circuit board, is desirable to optimally utilize the space taken up by the circuit board.
Conventionally, means for generating the high-frequency signal and the antenna unit including the antenna elements are formed on the same surface of a carrier or of a circuit board. This, however, takes up space on the surface of the carrier or of the circuit board which could also be used to form an antenna unit having a larger surface area. Furthermore, interference signals, which may impair the quality of the high-frequency signal to be emitted, may originate from the means for generating the high-frequency signal and the galvanic connections to the antenna elements.
German Patent Application No. DE 101 04 864 A1 describes a device for sending and/or receiving radar beams, which includes a circuit board having one antenna situated on one side, and electric circuits situated on the other side. Via a feed network designed in coplanar line technology, the at least one antenna is galvanically connected to the electric circuits.